Aims: The broad goal of this project is to identify genes which cause hereditary neuropathies. The project will investigate Tangier disease (TD) and Hereditary sensory neuropathy type-1 (HSN1) pedigrees using linkage analysis and positional cloning techniques. The underlying hypothesis is that these techniques will identify the disease-associated genes for TD and HSN1. The specific aims of the project are to: 1) establish gene linkage in a large Tangier Disease pedigree and develop a physical map of the linked region; 2) use the evolving physical map of chromosome 9 to refine the localization of the HSN1 region; 3) initiate a search for the TD and HSN1 genes within their respective mapped loci, through the identification of candidate genes within the two disease loci. Methods: In aim 1, we will carry out a genome wide screen to identify genetic markers (short tandem repeat polymorphisms of simple sequence markers (SSRs)) that segregate with TD and then use recombination analysis to refine the region of linkage. We will then use genomic DNA cloned into artificial chromosomes to construct a physical map of the linked region. In aim 2, we will initially confirm linkage of the HSN1 locus to markers D9S318 and D9S176 and then select artificial chromosomes whose cloned genomic DNA spans the region for further fine physical mapping. In aim 3, we will use available cDNA libraries and the artificial chromosomes, defined by the initial parts of the project, in various hybridization and amplification techniques to clone genes mapped to the loci of the two diseases. Furthermore, we will, using the Human Genome Database to identify any previously characterized genes mapping to the disease loci. Having identified the genes in this manner, we will screen them in the disease pedigrees, using single strand conformational polymorphism and straight sequencing and to detect any mutations. Significance: The identification of these disease- associated genes will: 1) elucidate the molecular defects underlying these two neuropathies; 2) increase our understanding of normal sensory nerve function; 3) in the case of TD, define a new gene or gene family crucial to high density lipoprotein and intracellular cholesterol metabolism.